Hydraulic brake



July 3o, 1935. E, G. CARROLL 2,009,433

HYDRAULIC BRAKE Filed March 4, 1932 :A P i; v 1 s. /C @gggnnul il H 6a iIN VEN TOR.

EUGENE GLARROLL BY /wx A TTORNEY brakes.

Patented July 30, 1935 UNITED STATES PATENT OFFICE HYDRAULIC BRAKEApplication March 4, 1932, serial N0.`59s,so7

1 Claim.

This invention relates to brakes and more particularly to hydraulicbrakes.

Hydraulic brake systems utilize liquids to transmit force from itssource of application to the In order that the transmission shall beeflicient and satisfactory, it is necessary that the liquid shall besubstantially incompressible and it is therefore necessary that it shallbe substantially free of air and other gases. The operation ofeliminating the gases from the' system is known as bleeding and isusually performed before the system is put into operation and as oftenthereafter as may be necessary. Heretofore, the operation of bleedinghas usually been accomplished by opening an outlet leading from eachofthe wheel cylinders in succession and forcing liquid through thesystem and out of said outlet. Such systems require one or more valveswithin the operating portion of the systems and inasmuch as valvessometimes become stuck, such systems aresometimes subject to operatingdiiilculties.

Furthermore, the valves employed are usually spring loaded to maintain acertain pressure. As the springs deteriorate with use, the pressureswhich are maintained vary with accompanying' disadvantages.

One of the objects of my invention is to provide an improved means forbleeding hydraulic brake systems.

A' further object is to provide a hydraulic brake e system normallymaintained under atmospheric pressure and not dependent for itsoperation upon yordinary valves or springs.

An important feature of my invention relates to theuse of a bleedinghose provided with a check valve and adapted to be used only during thebleeding operation and then adapted to be securedin turn to each of thewheel cylinders.

A further feature relates to means for sealing the wheel cylinders toinsure against the sucking in of air during the bleeding operation.

Further features relate to 'the construction of the wheel cylinders, themaster cylinder, and the supply reservoir all designed to contribute tothe eiiicient functioning of a hydraulic brake system which may bemaintained normally under atmospheric pressure and which does not dependfor its operation upon ordinary valves or upon springs.

The above and other objects and features of the invention includingvarious novel and desirable details of construction will be apparentfrom the following description of the two illustrative (Cl. Gil-54.5)

embodiments shown in the accompanying drawing, in which;

Figure 1 is a more or less diagrammatic view of a hydraulic brake systemshowing, the reservoir, master cylinder, wheel cylinder and bleedinghose 5 in section; and

Figure 2 is a fragmentary sectional view of a modied form of mastercylinder.

The system illustrated in Figure 1 includes a master cylinder II, areservoir I2 secured therel0 to, wheel cylinders such as I3 and suitableliquid pressure lines such as I4 connecting the master cylinder and theWheel cylinder. There is provided a bleeding hose I5 normally detachedfrom the wheel cylinder, but adapted during the 15 bleeding operation-tobe secured to each wheel cylinder in turn as it is shown attached to oneof the wheel cylinders in Figure 1.

The master cylinder generally designated II comprises a cylindricalcasting I6 formed with a 20 bore I'I' of uniform diameter and providedwith a relatively large inlet port I8 and a relatively restricted inletport I9. The forward end of the casting I6 has secured thereto an outletcap 2| screwed onto the casting and formed with an 25 I annular springseat 22 and with a tapped opening 23 to which there is secured a conduitforming a part of one of the fluid pressure lines I4. The spring 20seats at its forward end in the seat 22 and bears at its rear end on thepiston 26. The 30 spring serves to return the piston 26 when the footpressure on the pedal is released.

Mounted for reciprocation -in the cylinder I6 is a piston 24 formed witha rear head 25 and a forward head 26. Cups 21 and 28 are asso- 35 ciatedwith these heads and are seated in annu-r lar grooves 3I and 32 formedin suitable portions of the piston. Split spring collars such as 33 and34 serve to hold thev cups in position in their respective grooves. Thehead 26 is formed to 40 have a relatively loose lit in the bore I'I. Byreason thereof, liquid may, whenv needed, flow from the chamber 35(formed intermediate the heads 25 and 26) around the head 26 and pastthe forward cup 28 into the pressure chamber 36. 45

The piston 24 is hollow and is formed adjacent to its forward end withan enlarged recess 36 into which the spherical head 31 of the piston rod38 extends. The head 3l is secured in position by a spring collar 3Swhich is first loosely inserted and subsequently deformed by a punch tofasten the head securely in the recess. The rear end of the cylinder isformed with a groove in which a spring 40 is received, the springserving to limit the movement of the piston 24. The rear end of 55 thecylinder may be closed by a boot 4| and the reservoir I2 may be providedwith a oat 42 carrying an indicator 43 by which the level of the liquidin the reservoir is always apparent to th operator. The wheel cylinderI3 is formed of a substantially cylindrical casting 46 and a pair ofpistons 41 and 48, the pistonsare formed with annular grooves 49 and 5Iin which there are seated annular cup packings 52 and 53 and there maybe provided intermediate these packings the spring 54. The pressure lineI4 is connected to the interior of the cylinder by a port 55 and forpurposes of bleeding thereis provided a bleed opening 56 normally closedby a plug 51 and a screw 58. The plug 51 yis formed with a relativelylarge concentric tapped bore 9| into which the screw 58 is normallythreaded; with a restricted concentric bore 92 and with a transversebore 93 intersected by said bore 92. During the bleeding operation,however, the screw 58 is removed as it is shown, the plug 51' isloosened and a bleeding hose I5 is inserted in place of the screw 58..The bleeding hose I5 is provided with a one way outlet valve assembly6| including a check valve which may consist of a ball 63 normallymaintained on its seat by a spring 64 reacting on a plug 65 screwed intothe valve casing 66.

The pistons 41 and 48 are formed at their outer ends with flanges 61 and68 which overlie the ends of the cylinder 46 and which in the offposition of the brakes clamp packings 69 and 18 to form a fluid tightseal for the wheel cylinder I3. In the normal operation of thisembodiment of my invention pressure upon the foot pedal which isattached to the piston rod 38 moves the piston 24 forward in thecylinder I6 and thus forces liquid under pressure through the opening 23and the pressure line I4. The liquid is thus forced through the port 55into the wheel cylinder I3, thus spreading the pistons 41 and 48 andthrough said pistons acting to apply the brake shoes. Release of thepressure upon the pedal allows the return of the piston 24 and thesprings on the brakes cause the return of the pistons 41 and 48 to theirnormal inactive position. While the pistons are in their inactiveposition the packings 69 and 10 prevent the suction of air in the wheelcylinder. The return of the master piston 24 allows liquid from thereservoir I2 to be drawn through the port I8 past the cup 28 to thechamber 30, thus compensating for temperature changes, etc., but liquidcan at no time pass rearwardly from chamber 30 to chamber 35 past thecup 28. Upon the return of the piston to the normal inactive position,any excess liquid may return to the reservoir through the port I9.

In the bleeding operation, pressure upon the foot pedal forces liquidforward through the lines into the wheel cylinders and forces air andliquid out through the hose I5 past the check valve 6|. On the returnstroke the re-entrance of air is prevented by the check valve 6| andliquid is drawn into the chamber 38 and the forward part of the systempast lthe cup 28.'

In the modified form of my invention shown in Fig. 2, the forward head26a. of the piston 24a is extended rearwardly as at 21a so that in thenormal inactive position communication is cut off between the reservoirI2a and the recess 35a. "A spring 13 is provided for aiding in holdingthe cup 34a in position, and a spring loaded valve 14 is provided to`maintain a predetermined pressure within the system. The valve 14comprises a well formed by an annular upstanding projection 15 integralwith the cylinder I6a; a cap 16 formed with an opening 11 and screwedinto the projection 15; a valve member 8 I; and a spring 'I9 normallyurging the valve memberl upon its seat 18.

The operation of this embodiment of my invention is similar to thatdescribed above. However, a constant pre-determined superatmosphericpressure is maintained in the system by reason of the spring loadedvalve I4 and leaks which may develop in the rear part of the cylind-erwhile the apparatus is idle will drain the recess 35a only and will notat the same time drain the reservoir I2.

'I'he master cylinder and reservoir structure disclosed therein is alsodisclosed and is claimed in my copending application Serial No. 21,953,filed May 1'7, 1935. l

It is to be understood that the above described embodiments of myinvention are for the purpose of illustration only and Vvarious changesmay be made therein without departing from the spirit and scope of theinvention.

I claim:

In a hydraulic brake system a wheel cylinder provided with an inletopening and having an outlet opening formed with a conical Valve seat, aplug for said outlet opening provided with a conical end for seating onsaid valve seat and formed with a longitudinal bore and with a lateralbore adjacent to said conical end intersecting with saidlongitudinalbore, and a screw normally closing said longitudinal bore whereby whensaid conical end of the plug is seated on the conical valve seat and thescrew is inserted in said plug, a double seal is provided to preventescape of liquid or ingress of air, but when said plug is movedoutwardly of said outlet openingand said screw is removed, liquid may beforced out past said conical end through said lateral bore and throughsaid longitudinal bore to the atmosphere.

EUGENE G. CARROLL.

